Osteopathic physicians caring for patients with fibromyalgia syndrome (FM) often use osteopathic manipulative treatment (OMT) in conjunction with other forms of standard medical care. Despite a growing body of evidence on the efficacy of manual therapy for the treatment of selected acute musculoskeletal conditions, the role of OMT in treating patients with chronic conditions such as FM remains largely unknown. Twenty-four female patients meeting American College of Rheumatology criteria for FM were randomly assigned to one of four treatment groups: (1) manipulation group, (2) manipulation and teaching group, (3) moist heat group, and (4) control group, which received no additional treatment other than current medication. Participants' pain perceptions were assessed by use of pain thresholds measured at each of 10 bilateral tender points using a 9-kg dolorimeter, the Chronic Pain Experience Inventory, and the Present Pain Intensity Rating Scale. Patients' affective response to treatment was assessed using the Self-Evaluation Questionnaire. Activities of daily living were assessed using the Stanford Arthritis Center Disability and Discomfort Scales: Health Assessment Questionnaire. Depression was assessed using the Center for Epidemiological Studies Depression Scale. Significant findings between the four treatment groups on measures of pain threshold, perceived pain, attitude toward treatment, activities of daily living, and perceived functional ability were found. All of these findings favored use of OMT. This study found OMT combined with standard medical care was more efficacious in treating FM than standard care alone. These findings need to be replicated to determine if cost savings are incurred when treatments for FM incorporate nonpharmacologic approaches such as OMT.